Feign是什么,feign作用

feign模块（代替ribbon）

构建工程步骤：

1. pom.xml

<?xml version="1.0" encoding="UTF-8"?><project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.1.6.RELEASE</version><relativePath/> </parent><groupId>com.mqb</groupId><artifactId>spring-clloud-consumer-feign</artifactId><version>0.0.1-SNAPSHOT</version><name>spring-clloud-consumer-feign</name><description>Demo project for Spring Boot</description><properties><java.version>1.8</java.version><spring-cloud.version>Greenwich.SR2</spring-cloud.version></properties><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-netflix-eureka-client</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-openfeign</artifactId></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency></dependencies><dependencyManagement><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-dependencies</artifactId><version>${spring-cloud.version}</version><type>pom</type><scope>import</scope></dependency></dependencies></dependencyManagement><build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin></plugins></build></project>

2. application.properties

server.port=8088##微服务名spring.application.name=application-dept##eurekaeureka.client.register-with-eureka=falseeureka.client.service-url.defaultZone=http://eureka-server7001.com:7001/eureka/,http://eureka-server7002.com:7002/eureka/

3. 主类

package com.mqb.consumerfeign;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.cloud.netflix.eureka.EnableEurekaClient;import org.springframework.cloud.openfeign.EnableFeignClients;@SpringBootApplication@EnableFeignClients(basePackages = "com.mqb.consumerfeign.providerdept")@EnableEurekaClientpublic class SpringClloudConsumerFeignApplication {public static void main(String[] args) {SpringApplication.run(SpringClloudConsumerFeignApplication.class, args);}}

4.其他代码

4.1 Dept.java

package com.mqb.consumerfeign.providerdept.entity;import lombok.Getter;import lombok.Setter;import lombok.ToString;@ToString@Getter@Setterpublic class Dept { private Long deptId; private String name; private String dbSource;}

4.2 controller

package com.mqb.consumerfeign.providerdept.controller;import com.mqb.consumerfeign.providerdept.entity.Dept;import com.mqb.consumerfeign.providerdept.service.DeptService;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Controller;import org.springframework.web.bind.annotation.*;@Controllerpublic class DeptController_Consumer { @Autowired private DeptService deptService; @ResponseBody @RequestMapping(value = "/getDept/{id}",method = RequestMethod.GET) public Dept getDept(@PathVariable("id") Long deptId){ return deptService.getDeptById(deptId); }}

4.3 service

package com.mqb.consumerfeign.providerdept.service;import com.mqb.consumerfeign.providerdept.entity.Dept;import org.springframework.cloud.openfeign.FeignClient;import org.springframework.web.bind.annotation.PathVariable;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RequestMethod;@FeignClient("PROVIDER")public interface DeptService { @RequestMapping(value = "/getDept/{id}",method = RequestMethod.GET) // "/{id}"不能少 public Dept getDeptById(@PathVariable("id")Long deptId); //@PathVariable注解不能少}

千辛万苦改成上面这样，终于成功了。

接下来才是重点，可能也是大家最想看的。

feign的使用一不小心就容易踩坑，我之前在网上搜了一大堆博客，但错误和漏洞很多，所以再此我把我所知道并且验证过的坑给列出来：

1. 我搜了很多博客都说必须类必须使用@RestController，然而我的controller类使用@Controller以及方法使用@ResponseBody组合依然可以正确运行，所以和controller类是否使用@RestController无关。

2. 我试了把DeptController_Consumer中@RequestMapping注解的method = ResquestMethod.GET去掉，运行没问题，DeptService中的method去掉也没问题。至于delete和post方法等还没试。所以和@Request注解是否method无关。

3. 把DeptService中RequestMapping中路径的/{id}去掉，报错！！！抛出feign.FeignException$NotFound: status 404 reading xxx异常。所以“路径/{id}”不能省

4. 把DeptService中getDeptById方法形参去掉@PathVariable("id")注解，报错！！！抛出feign.FeignException$NotFound: status 404 reading xxx异常。所以@PathVariable("id")不能省。

5. 试试controller和service路径不一样会怎么样。

修改controller访问路径，路径前面添加“/consumer”，变成/consumer/getDept/{id},而service路径保持getDept/{id}不变。

测试结果：访问loalhost:8080/consumer/getDept/1，结果说明可以访问，所以说明feign模块的controller和service路径不需要相同甚至无关。但是feign模块的service和服务提供模块的controller方法路径必须一致。访问结果如下。

以上五点是我自己踩过的坑，也验证了。如果还有其他，欢迎补充。

最后，如果想运行本篇的feign代码还需要用到的上篇博客中的四个模块代码：

spring-cloud-eureka-server-7001，

spring-cloud-eureka-server-7002，

spring-cloud-provider-8001，

完整代码参考上篇博客：https://blog.csdn.net/weixin_42130471/article/details/97617025